Polycrystalline ultra-hard constructions, such as polycrystalline diamond (PCD) materials and PCD elements formed therefrom, are well known in the art. Conventional PCD is formed by subjecting diamond grains to processing conditions of extremely high pressure and high temperature in the presence of a suitable solvent catalyst material, wherein the solvent catalyst material promotes desired intercrystalline diamond-to-diamond bonding between the grains, thereby forming a PCD structure.
The solvent catalyst material can be combined with the diamond grains prior to processing or the solvent catalyst material can be provided from an outside source, e.g., from an adjacent substrate body or the like that contains the solvent catalyst material, by infiltration during processing. The resulting PCD structure produces enhanced properties of wear resistance and hardness, making PCD materials extremely useful in aggressive wear and cutting applications where high levels of wear resistance and hardness are desired.
Solvent catalyst materials typically used for forming conventional PCD include metals selected from Group VIII of the Periodic table, with cobalt (Co) being the most common. Conventional PCD can comprise from 85 to 95% by volume diamond and a remaining amount of the solvent catalyst material. The solvent catalyst material is disposed within interstitial regions of the PCD microstructure that exist between the bonded together diamond grains or crystals.
PCD as used in certain industrial wear and/or cutting applications, such as cutting elements in subterranean drill bits, are provided in the form of a compact comprising the PCD material attached to a substrate. The PCD material is positioned on the substrate at a location to engage the surface to be cut or worn, and the substrate is provided for the purpose of facilitating attachment of the PCD compact to the end use wear and/or cutting device. Conventional PCD cutters comprise a PCD body that is joined with a metallic or cermet substrate, e.g., such as one formed from cemented tungsten carbide. Such conventional PCD compacts are formed by placing a desired substrate next to the diamond grain volume and subjecting the combination to high pressure and high temperature (HPHT) processing.
When used as a cutting element in a drill bit, the PCD compact is attached to a portion of the drill bit by welding or brazing. More specifically, the PCD compact is attached to the drill bit by welding or brazing the substrate portion of the PCD compact to a desired portion of the drill bit. Conventional PCD compacts configured for use as such cutting elements have a generally cylindrical shape. Accordingly, when attached for use with a drill bit, the cylindrical PCD compact substrate is brazed or welded to the desired body portion of the drill bit.
A problem known to exist with such conventional PCD compacts configured as cutting elements for use with subterranean drill bits is that the PCD compacts fracture during the process of drilling, causing the PCD compact to break away from and fall off of the drill bit body. Such fracturing is known to occur at the point of attachment between the PCD compact substrate and the drill bit.
In addition to PCD, another form of polycrystalline diamond conventionally used for its desired properties of wear and/or abrasion resistance is one that is substantially free of the catalyst material used to form the PCD. This type of polycrystalline diamond is known as thermally stable polycrystalline diamond (TSP) because it is also known to have improved thermal properties when compared to conventional PCD. While such TSP materials do provide certain performance advantages, the desired lack of catalyst material makes it difficult to form a compact construction having a substrate attached to the TSP material. The presence of a substrate is desired to facilitate attachment of the construction to an end-use wear and/or cutting device. The substrates for such TSP construction are conventionally attached to the TSP material by welding or brazing, which attachment has shown to be vulnerable to failure in operation.
It is, therefore, desired that polycrystalline ultra-hard constructions be configured in a manner that is specially engineered and designed to provide an enhanced degree of contact between a PCD compact and the wear and/or cutting device to maximize the attachment therebetween, and thereby minimize and/or eliminate the possibility of the PCD compact fracturing or otherwise becoming detached from the wear and/or cutting device during use. It is desired that the PCD compact be configured in a manner that contributes to the overall strength of the PCD compact itself. It is further desired that the polycrystalline ultra-hard constructions be configured in a manner engineered to place the polycrystalline ultra-hard material and substrate attached thereto, in a state of compression to thereby improve the attachment strength between the polycrystalline ultra-hard body and a substrate included in the construction.